Beam-combining laser beam source device

ABSTRACT

A beam-combining laser beam source device comprising an airtight housing and a laser beam source unit housed in the housing. The laser beam source unit comprises laser beam sources and collimator optical systems respectiely positioned in optical paths of laser beams, which are radiated from the laser beam sources, in order to collimate the laser beams. Optical path adjusting elements are respectively positioned in the optical paths of the laser beams in order to radiate the laser beams along optical paths parallel and close to one another. The laser beam sources, the collimator optical systems, and the optical path adjusting elements are supported on a single support. The housing is provided with a temperature sensor, which detects the temperature in the housing, and temperature adjusting elements which heat or chill the housing on the basis of control of the temperature sensor so that the temperature in the housing is kept constant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to a beam-combining laser beam sourcedevice wherein laser beams produced by a plurality of laser beamsources, such as semiconductor lasers which have a low power output, arecombined so as to multiply the power of the individual laser beamsources. This invention particularly relates to a beam-combining laserbeam source device wherein a high accuracy of laser beam combination iskept consistent.

2. Description of the Prior Art

Light beam scanning apparatuses wherein a laser beam is deflected by alight deflector in order to scan a surface with the laser beam haveheretofore been widely used in, for example, scanning recordingapparatuses and scanning read-out apparatuses. In such light beamscanning apparatuses, it is desired that a plurality of laser beams becombined so as to obtain laser beams having a high intensity and thatthose laser beams having a high intensity be used as scanning light inorder to, for example, increase the speed at which the informationrecorded on a surface to be scanned is recorded or read out. Combinationof the laser beams is required particularly when semiconductor lasersare used as the laser beam sources. Specifically, a semiconductor laserhas various advantages over a gas laser or the like in that thesemiconductor laser is small in size, cheap and consumes little power,and that the laser beam can be modulated directly when the drive currentapplied to the semiconductor laser is changed.

However, the output power of the semiconductor laser is low (20 mW to 30mW) when the semiconductor laser is operated in order to continuouslyradiate the laser beam. Therefore, the semiconductor laser is notsuitable for use in a light beam scanning apparatus wherein scanninglight having a high energy is necessary, for example: a scanningrecording apparatus wherein information is recorded on a recordingmaterial which has a low sensitivity, such as a draw material (a metalfilm, an amorphous film, or the like).

On the other hand, when certain kinds of phosphors are exposed toradiation such as X-rays, α-rays, β-rays, γ-rays, cathode rays orultraviolet rays, they store part of the energy of the radiation. Then,when the phosphor which has been exposed to the radiation is exposed tostimulating rays such as visible light, light is emitted by the phosphorin proportion to the amount of energy stored during exposure to theradiation. A phosphor exhibiting such properties is referred to as astimulable phosphor. In U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318and 4,387,428 and Japanese Unexamined Patent Publication No.56(1981)-11395, use of a stimulable phosphor in a radiation imagerecording and reproducing system was proposed. Specifically, a sheetprovided with a layer of the stimulable phosphor (hereinafter referredto as a stimulable phosphor sheet) is first exposed to radiation whichhas passed through an object such as the human body in order to store aradiation image of the object thereon, and is then scanned with astimulating ray such as a laser beam which cause it to emit light inproportion to the amount of energy stored during exposure to theradiation. The light emitted by the stimulable phosphor sheet uponstimulation thereof is photoelectrically detected and converted into anelectric image signal, and the image signal is used to reproduce theradiation image of the object as a visible image on a recording materialsuch as photographic film, a display device such as a cathode ray tube(CRT), or the like.

In the aforesaid radiation image recording and reproducing system, it isdesired to use a light beam scanning apparatus, wherein a semiconductorlaser is used, in order to scan the stimulable phosphor sheet on which aradiation image has been stored, thereby to read out the radiationimage. However, in order to quickly read out the radiation image fromthe stimulable phosphor sheet, it is necessary to irradiate stimulatingrays which have a sufficiently high energy onto the stimulable phosphorsheet. Accordingly, it is not always possible to use a light beamscanning apparatus, wherein a semiconductor laser is used, in order toread out an image in the radiation image recording and reproducingsystem.

In order to obtain a scanning laser beam having a sufficiently highenergy from a semiconductor laser, or the similar lasers, having a lowpower outputs, a plurality of laser beam sources may be used, and laserbeams radiated from the laser beam sources may be combined so as tomultiply the power of the individual laser beam sources.

In general, in order to combine the laser beams produced by a pluralityof laser beam sources, the laser beams produced by the laser beamsources are collimated respectively by collimator lenses, guided alongoptical paths parallel and close to one another, and converged to acommon spot by a converging lens. For example, in Japanese PatentApplication No. 63(1988)-35836 a beam-combining laser beam source unitis provided with a plurality of laser beam sources and which efficientlycombines laser beams. The proposed laser beam source unit comprises aplurality of laser beam sources, collimator optical systems positionedin optical paths of laser beams, which are radiated from the laser beamsources, in order to collimate the laser beams, and optical pathadjusting elements respectively positioned in the optical paths of thelaser beams in order to radiate the laser beams along optical pathsparallel and close to one another. The laser beam sources, thecollimator optical systems, and the optical path adjusting elements aresupported on a single support means. With the proposed laser beam sourceunit, when the laser beams radiated from the laser beam source unit arecaused to impinge upon a converging lens, the laser beams can beconverged to a single spot at a desired position.

In order to accurately combine the laser beams in the laser beam sourceunit described above, it is necessary to accurately adjust the positionsof the optical elements of the laser beam source unit so that the laserbeams radiated from the laser beam source unit are collimated and followpredetermined optical paths which are parallel to one another. For thispurpose, it is necessary to adjust the temperature of the whole laserbeam source unit so that it is uniform. Specifically, if the temperatureof the laser beam source unit were not uniform, the holding means wouldbe deformed, and therefore the accuracy of the positions of thecollimator optical systems and the optical path adjusting elements wouldbecome deteriorated. As a result, the condition in which the laser beamsare radiated from the laser beam source unit varies, and the laser beamscannot be combined accurately at a predetermined position. For example,in cases where the laser beam source unit is used as a means to generatescanning light which is used to read out or reproduce a radiation imagein the radiation image recording and reproducing system described above,scanning light comprising the laser beams combined in a desirable mannercould not be obtained if a temperature difference on the order ofapproximately 1° C. arose with the laser beam source unit.

In order to make the temperature of the laser beam source unit uniform,providing the laser beam source unit with heaters and a temperaturesensor, and to control the operations of the heaters based on thedetection of the temperature sensor so that the temperature of the laserbeam source unit is kept at a constant value (for example, 48° C.) areconsidered.

However, in general, the temperature of ambient air around the laserbeam source unit which is being operated is lower than the temperatureof the laser beam source unit. Therefore, in cases where the laser beamsource unit is located so that it is in contact with ambient air, eventhough the temperature of the laser beam source unit is controlled inthe manner described above, the laser beam source unit is cooled by theambient air, so that the temperature of the laser beam source unit inpositions close to the heaters and positions remote therefrom.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide abeam-combining laser beam source device wherein the temperature of alaser beam source unit is kept uniform without being adversely affectedby ambient air.

Another object of the present invention is to provide a beam-combininglaser beam source device wherein a high accuracy of laser beamcombination is kept consistent.

The present invention provides a first beam-combining laser beam sourcedevice which comprises:

(i) an airtight housing, and

(ii) a laser beam source unit which is housed in said housing and whichcomprises:

(a) a plurality of laser beam sources,

(b) collimator optical systems respectively positioned in optical pathsof laser beams, which are radiated from the laser beam sources, in orderto collimate the laser beams,

(c) optical path adjusting elements respectively positioned in theoptical paths of the laser beams in order to radiate the laser beamsalong optical paths parallel and close to one another, and

(d) a support means which supports said laser beam sources, saidcollimator optical systems and said optical path adjusting elements,

wherein said housing is provided with a temperature sensor, whichdetects the temperature in said housing, and temperature adjustingelements which heat or chill said housing on the basis of control ofsaid temperature sensor, so that the temperature in said housing is keptconstant.

With the first beam-combining laser beam source device in accordancewith the present invention, the laser beam source unit is housed in thehousing, and the temperature in the housing is adjusted so that it iskept constant regardless of the temperature of ambient air. Therefore,the temperature of the laser beam source unit housed in the housing canbe kept at a predetermined value without being adversely affected byambient air. The laser beam source unit may be provided with atemperature adjusting means which is independent from the temperaturesensor and the temperature adjusting elements of the housing, and whichadjusts the temperature of the laser beam source unit when the operationof the beam-combining laser beam source device is begun.

The present invention also provides a second beam-combining laser beamsource device which comprises:

(i) an airtight housing,

(ii) a laser beam source unit which is housed in said housing and whichcomprises:

(a) a plurality of laser beam sources,

(b) collimator optical systems respectively positioned in optical pathsof laser beams, which are radiated from the laser beam sources, in orderto collimate the laser beams,

(c) optical path adjusting elements respectively positioned in theoptical paths of the laser beams in order to radiate the laser beamsalong optical paths parallel and close to one another, and

(d) a support means which supports said laser beam sources, saidcollimator optical systems, and said optical path adjusting elements,

(iii) a temperature sensor which detects the temperature of said laserbeam source unit, and

(iv) at least one heating means which is secured to said housing andwhich radiates heat to said laser beam source unit on the basis ofcontrol of said temperature sensor so that the temperature of said laserbeam source unit is kept constant.

With the second beam-combining laser beam source device in accordancewith the present invention, the laser beam source unit is housed in thehousing, and is positively heated by the heating means, which is securedto the housing, so that the temperature of the laser beam source unit iskept constant. Therefore, the adverse effects of the ambient air do notcause the temperature of the laser beam source unit to fluctuate. Theterm "heating means" as used herein means a means which heats the laserbeam source unit so that the temperature thereof is kept higher than thetemperature of the ambient air.

The present invention further provides a third beam-combining laser beamsource device which comprises:

(i) an airtight housing,

(ii) a laser beam source unit which is housed in said housing and whichcomprises:

(a) a plurality of laser beam sources,

(b) collimator optical systems respectively positioned in optical pathsof laser beams, which are radiated from the laser beam sources in orderto collimate the laser beams,

(c) optical path adjusting elements respectively positioned in theoptical paths of the laser beams in order to radiate the laser beamsalong optical paths parallel and close to one another, and

(d) a support means which supports said laser beam sources, saidcollimator optical systems and said optical path adjusting elements,

wherein the pressure in said housing is not higher than 0.5 atm.

Part of heat transfer between the laser beam source unit and ambient airis effected by convection of air around the laser beam source unit. Withthe third beam-combining laser beam source device in accordance with thepresent invention wherein the pressure around the laser beam source unitis reduced, it is possible to prevent convection and to minimize releaseof heat from the laser beam source unit.

The present invention still further provides a fourth beam-combininglaser beam source device which comprises:

(i) an airtight housing,

(ii) a laser beam source unit which is housed in said housing and whichcomprises:

(a) a plurality of laser beam sources,

(b) collimator optical systems respectively positioned in optical pathsof laser beams, which are radiated from the laser beam sources in orderto collimate the laser beams,

(c) optical path adjusting elements respectively positioned in theoptical paths of the laser beams in order to radiate the laser beamsalong optical paths parallel and close to one another, and

(d) a support means which supports said laser beam sources, saidcollimator optical systems and said optical path adjusting elements,

wherein the emissivity of the outer surface of said support means is notlarger than 0.5, and/or the emissivity of the inner surface of saidhousing is not larger than 0.5.

With the fourth beam-combining laser beam source device in accordancewith the present invention, the emissivity of the outer surface of thesupport means and/or the emissivity of the inner surface of the housingis restricted to a value not larger than 0.5. Therefore, it is possibleto prevent heat emission from the laser beam source unit through thehousing to the exterior, thereby to prevent the laser beam source unitfrom being chilled by ambient air. In cases where the emissivity of theinner surface of the housing is restricted to a value not larger than0.5, the inner surface outside of the part of the housing through whichlaser beams pass is treated so that it has a desired emissivity.

As described above, with the first to fourth beam-combining laser beamsource devices in accordance with the present invention, it is possibleto prevent the laser beam source unit from being chilled by ambient air.Therefore, it is possible to eliminate the problem of the thetemperature of the laser beam source unit becoming nonuniform and theaccuracy of the positions of the optical elements of the laser beamsource unit becoming deteriorated. Accordingly, a high accuracy of laserbeam combination can be kept consistent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an embodiment of the beam-combininglaser beam source device in accordance with the present invention,

FIG. 2 is a perspective view showing the laser beam source unit in theembodiment of FIG. 1,

FIG. 3 is a sectional view taken along line X--X in FIG. 1,

FIG. 4 is a schematic view showing cross-sections of laser beamsradiated from the laser beam source unit shown in FIG. 2, and

FIGS. 5, 6 and 7 are schematic views showing further embodiments of thebeam-combining laser beam source device in accordance with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinbelow be described in further detailwith reference to the accompanying drawings.

With reference to FIG. 1, an embodiment of the beam-combining laser beamsource device in accordance with the present invention comprises anairtight housing 10 constituted of a metal material or the like, and alaser beam source unit 1 which is housed in the housing 10 and which isprovided with a plurality of semiconductor lasers. A plurality of laserbeams radiated from the laser beam source unit 1 along optical pathsparallel and close to one another are radiated through an emissionwindow 10A to the area outside of the housing 10. The configuration ofthe laser beam source unit 1 will be described hereinbelow withreference to FIG. 2.

The laser beam source unit 1 comprises, by way of example, tensemiconductor lasers 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, 3I and 3J which arepositioned in two rows and secured to an upper plate 2A of support means2 so that their axes of laser beam emission are parallel one another. Apair of middle plates 2B, 2B are secured to the middle portion of a wallmember 2D which supports the upper plate 2A. Ten concave lenses 4, 4, .. . are secured to the middle plates 2B, 2B, five lenses on each plate,so that they face the semiconductor lasers 3A through 3J. Also, a pairof mirror holding plates 2G, 2G (only one of the plates is shown) aresecured to the lower portion of the wall member 2D. Ten reflectingmirrors 5, 5, . . . which act as optical path adjusting elements aresecured to the mirror holding plates 2G, 2G, five mirrors on each plate,so that the reflecting mirrors 5, 5, . . . face the concave lenses 4, 4,. . . The semiconductor lasers 3A through 3J, the concave lenses 4, 4, .. . and the reflecting mirrors 5, 5, . . . are positioned symmetricallywith respect to the wall member 2D. A first side plate 2E is secured toone side of the wall member 2D, and a second side plate 2F whichsupports a polarization beam splitter and a halfwave plate, which willbe described later, is secured to the other side of the wall member 2D.Also, a lower plate 2C is secured to the bottom face of the wall member2D. In the laser beam source unit 1 of this embodiment, the supportmeans 2 is constituted of the upper plate 2A, the middle plate 2B, thelower plate 2C, the wall member 2D, the first side plate 2E, the secondside plate 2F, and the mirror holding plates 2G, 2G.

Convex lenses 6, 6, . . . (not shown in FIG. 2) are provided inside ofthe upper plate 2A so that they face the semiconductor lasers 3A through3J. (By way of example, FIG. 3 shows the convex lens 6 facing thesemiconductor laser 3A.) In this laser beam source unit 1, a collimatoroptical system is constituted of the concave lens 4 and the convex lens6. As shown in FIG. 3, a laser beam 3a produced by the semiconductorlaser 3A is passed through and collimated by the collimator opticalsystem. In the same manner, laser beams 3b through 3j produced by thesemiconductor lasers 3B through 3J are collimated by correspondingcollimator optical systems provided in the optical paths of the laserbeams 3b through 3j.

The laser beams 3a, 3c, 3e, 3g and 3i after being collimated arereflected by the reflecting mirrors 5, 5, . . . provided therebelow, andimpinge upon a polarization beam splitter 7. The semiconductor lasers3A, 3C, 3E, 3G and 3I are positioned so as to radiate the laser beams3a, 3c, 3e, 3g and 3i in a single plane. Also, the reflecting mirrors 5,5, . . . provided in the optical paths of the laser beams 3a, 3c, 3e, 3gand 3i are held by the mirror holding plate 2G, which has a step-likeupper face, so that they are vertically deviated little by little fromone another as shown in FIG. 2. Therefore, the positions from which thelaser beams 3a, 3c, 3e, 3g and 3i are reflected by the reflectingmirrors 5, 5, . . . vary little by little only in the verticaldirection, and the laser beams 3a, 3 c, 3e, 3g and 3i after beingreflected by the reflecting mirrors 5, 5, . . . follow optical pathswhich are parallel and very close to one another in the verticaldirection. Also, on the rear side of the wall member 2D, laser beams 3b,3d, 3f, 3h and 3j, produced by the semiconductor lasers 3B, 3D, 3F, 3Hand 3J, are reflected by the reflecting mirrors 5, 5, . . . and thenfollow optical paths which are parallel and very close to one another inthe vertical direction. As for the laser beams produced by each pair ofthe semiconductor lasers provided facing each other with the wall member2D intervening therebetween (i.e. the laser beams 3a and 3b, the laserbeams 3c and 3d, and so on), the heights of the respective pairs oflaser beams are equal to each other after the laser beams are reflectedby corresponding reflecting mirrors 5, 5. Furthermore, the semiconductorlasers 3A through 3J are secured to the upper plate 2A so that thedirections of polarization of the laser beams 3a through 3j, after beingreflected by the reflecting mirrors 5, 5, . . . , are the same (i.e. thedirection coincides with the direction indicated by the arrow "a" inFIG. 2). The second side plate 2F is provided with openings throughwhich the laser beams 3a through 3j, after being reflected by thereflecting mirrors 5, 5, . . . , pass.

The polarization beam splitter 7 reflects light polarized in thedirection indicated by the arrow "a". Therefore, the laser beams 3a, 3c,3e, 3g and 3i are reflected by the polarization beam splitter 7. On theother hand, the laser beams 3b, 3d, 3f, 3h and 3j are reflected by amirror 8 so that the directions of their optical paths are changed by anangle of approximately 90°. Then, the laser beams 3b, 3d, 3f, 3h and 3jare passed through a halfwave plate 9 so that the direction ofpolarization is changed by an angle of 90°, and the laser beams 3b, 3d,3f, 3h and 3j are converted to light polarized in the directionindicated by the arrow "b". The polarization beam splitter 7 transmitslight polarized in the direction indicated by the arrow "b". Therefore,the laser beams 3b, 3d , 3f, 3h and 3j after being polarized in thedirection indicated by the arrow "b", pass through the polarization beamsplitter 7. The laser beam 3b is radiated along the same optical path asthe laser beam 3a, and the laser beam 3d is radiated along the sameoptical path as the laser beam 3c. Also, the laser beam 3f is radiatedalong the same optical path as the laser beam 3e, the laser beam 3h isradiated along the same optical path as the laser beam 3g, and the laserbeam 3j is radiated along the same optical path as the laser beam 3i.FIG. 4 shows cross-sections of the laser beams 3a through 3j radiatedalong the optical paths parallel and close to one another.

Reverting to FIG. 1, the housing 10 of the beam-combining laser beamsource device is provided with the emission window 10A through which thelaser beams 3a through 3j produced by the laser beam source unit 1 areradiated to the area outside of the housing 10. The emission window 10Ashould preferably be subjected to antireflection coating, and/orinclined with respect to the incident laser beams 3a through 3j so thatno light is reflected by the emission window to the semiconductor lasersand causes noise.

In this embodiment, the housing 10 is provided with a plurality ofheaters 11, 11, . . . , which act as temperature adjusting elements, anda temperature sensor 12, which keeps the temperature of the whole laserbeam source unit 1 constant. The heaters 11, 11, . . . are embedded inthe walls of the housing 10 in order to uniformly heat the whole areainside of the housing 10. The temperature in the housing 10 heated bythe heaters 11, 11, . . . is detected by the temperature sensor 12. Thetemperature sensor 12 turns off the heaters 11, 11, . . . when thedetected value is higher than a predetermined temperature, and turns onthe heaters 11, 11, . . . when the detected value is lower than thepredetermined value. The predetermined temperature should be set so thatthe temperature in the housing 10 is kept higher than the ambienttemperature at the location of the beam-combining laser beam sourcedevice regardless of fluctuations of the ambient temperature. Becausethe laser beam source unit 1 is housed in the airtight housing 10 andthe temperature in the housing 10 is kept constant, the temperature ofthe laser beam source unit 1 can be kept constant without being loweredby the ambient air, and can be prevented from varying between differentparts of the laser beam source unit 1. In this embodiment, as shown inFIG. 2, heaters 13, 13 are mounted on the side plates 2E and 2F of thelaser beam source unit 1, one heater on each side plate. (Only theheater 13 on the side plate 2F is shown in FIG. 2.) Also, a temperaturesensor 14 is mounted on the upper plate 2A in order to directly adjustthe temperature of the laser beam source unit 1 when the operation ofthe beam-combining laser beam source device is begun. Specifically, whenthe operation of the beam-combining laser beam source device is begun,the laser beam source unit 1 is directly heated by the heaters 13, 13 inorder to quickly raise the temperature of the laser beam source unit 1to approximately the predetermined temperature at which the temperaturein the housing 10 is to be kept by heating of the heaters 11, 11, . . .in the housing 10. Therefore, the time required to start the operationof the beam-combining laser beam source device can be shortened. Incases where the operation of the beam-combining laser beam source deviceneed not be started so quickly, the heaters 13, 13 and the temperaturesensor 14 of the laser beam source unit 1 may be omitted. Also, in caseswhere the ambient temperature around the beam-combining laser beamsource device is very high and exceeds the set temperature of thehousing 10, instead of the heaters 11, 11, . . . , cooling elements maybe provided as the temperature adjusting elements of the housing 10 inorder to keep the temperature in the housing 10 at a value lower thanthe ambient temperature.

Another embodiment of the beam-combining laser beam source device inaccordance with the present invention will be described hereinbelow withreference to FIG. 5.

The beam-combining laser beam source device shown in FIG. 5 comprisesheat radiating means 15, 15, . . . which are mounted on, by way ofexample, the inner side surface of the housing 10 in order to radiateheat to the inward side of the housing 10, and a temperature sensor 16which is mounted on the laser beam source unit 1. The heat radiatingmeans 15, 15, . . . heat the laser beam source unit 1 so that the laserbeam source unit 1 is kept at a predetermined temperature which ishigher than the ambient temperature. The temperature sensor 16 detectsthe temperature of the laser beam source unit 1 and turns the heatradiating means 15, 15, on and off . . . so that the detectedtemperature becomes constant. The temperature sensor 16 may directly orindirectly detect the temperature of the laser beam source unit 1, andneed not necessarily be mounted on the laser beam source unit 1. Anynumber of heat radiating means 15, 15, . . . may be located at arbitrarypositions on the inner surface of the housing 10 insofar as they canradiate heat to the whole area of the laser beam source unit 1.

In the two embodiments described above, the support means 2 of the laserbeam source unit 1 should preferably be constituted of a material suchas metal which has a high thermal conductivity.

A further embodiment of the beam-combining laser beam source device inaccordance with the present invention will be described hereinbelow withreference to FIG. 6. This embodiment is constituted to prevent heat fromescaping by radiation from the beam-combining laser beam source deviceto the ambient air. Specifically, the temperature of the laser beamsource unit 1 is kept constant by heaters 17, 17 and a temperaturesensor 18, which are mounted on the laser beam source unit 1. Also, anouter surface 2a of the support means 2 of the laser beam source unit 1and an inner surface 10a of the housing 10 are treated so that thesurfaces 2a and 10a have emissivities not larger than 0.5. For example,in order to form the surfaces 2a and 10a having emissivities not largerthan 0.5, the support means 2 and the housing 10 are constituted of ametal such as duralumin, and their surfaces are planished. The surfacesof the optical elements of the laser beam source unit 1, other than theparts through which the laser beams pass, may also be treated in thesame manner as the outer surface 2a of the support means 2 so that theemissivities of said surfaces are not larger than 0.5. Furthermore, anouter surface 10b of the housing 10 may be treated in the same manner asthe inner surface 10a so that the outer surface 10b has an emissivitynot larger than 0.5. With this embodiment, because the outer surface ofthe laser beam source unit 1 and the inner surface of the housing 10 hasemissivities not larger than 0.5, heat of the laser beam source unit 1does not readily escape from the laser beam source unit 1 or the housing10 to the outward side of the beam-combining laser beam source device.Therefore, the temperature of the laser beam source unit 1 can be keptconstant. Alternatively, either one of the outer surface of the laserbeam source unit 1 or the inner surface of the housing 10 may have anemissivity not larger than 0.5.

A still further embodiment of the beam-combining laser beam sourcedevice in accordance with the present invention will be describedhereinbelow with reference to FIG. 7. In this embodiment, a suctionmeans 19 is connected to the housing 10 in order to evacuate the housing10 so that the pressure therein is kept at a value not larger than 0.5atm. Because the pressure in the housing 10 is kept low, air convectionis prevented from arising in the housing 10 when the temperature of thelaser beam source unit 1 is adjusted to a high value by the heaters 17,17 and the temperature sensor 18, which are mounted on the laser beamsource unit 1. Therefore, it is possible to prevent heat from escapingthrough convection to the outward side of the beam-combining laser beamsource device. Also, when air convection in the housing 10 is minimized,it is possible to eliminate the problem of the positions of the laserbeams fluctuating due to sway of air. Evacuation of the housing 10 inaccordance with this embodiment may be combined with the embodimentsshown in FIGS. 1, 5 and 6.

We claim:
 1. A beam-combining laser beam source device whichcomprises:(i) an airtight housing, and (ii) a laser beam source unitwhich is housed in said housing and which comprises:(a) a plurality oflaser beam sources, (b) collimator optical systems respectivelypositioned in optical paths of laser beams, which are radiated from thelaser beam sources in order to collimate the laser beams, (c) opticalpath adjusting elements respectively positioned in the optical paths ofthe laser beams in order to radiate the laser beams along optical pathsparallel and close to one another, and (d) a support means whichsupports said laser beam sources, said collimator optical systems, andsaid optical path adjusting elements, wherein said housing is providedwith a temperature sensor, which detects the temperature in saidhousing, and temperature adjusting elements which heat or chill saidhousing on the basis of control of said temperature sensor so that thetemperature in said housing is kept constant.
 2. A device as defined inclaim 1 wherein said laser beam source unit is provided with atemperature adjusting means which is independent from said temperaturesensor and said temperature adjusting elements of said housing, andwhich directly adjusts the temperature of said laser beam source unitwhen the operation of the beam-combining laser beam source device isbegun.
 3. A device as defined in claim 1 wherein said support means isconstituted of a material having a high thermal conductivity.
 4. Abeam-combining laser beam source device which comprises:(i) an airtighthousing, (ii) a laser beam source unit which is housed in said housingand which comprises:(a) a plurality of laser beam sources, (b)collimator optical systems respectively positioned in optical paths oflaser beams, which are radiated from the laser beam sources, in order tocollimate the laser beams, (c) optical path adjusting elementsrespectively positioned in the optical paths of the laser beams in orderto radiate the laser beams along optical paths parallel and close to oneanother, and (d) a support means which supports said laser beam sources,said collimator optical systems, and said optical path adjustingelements, (iii) a temperature sensor which detects the temperature ofsaid laser beam source unit, and (iv) at least one heating means whichis secured to said housing and which radiates heat to said laser beamsource unit on the basis of control of said temperature sensor so thatthe temperature of said laser beam source unit is kept constant.
 5. Adevice as defined in claim 4 wherein said support means is constitutedof a material having a high thermal conductivity.